Fix for Symbol#to_proc ArgumentError issue

lib/blueprinter/extractors/block_extractor.rb

@@ -6,7 +6,31 @@ module Blueprinter
   # @api private
   class BlockExtractor < Extractor
     def extract(_field_name, object, local_options, options = {})
-      options[:block].call(object, local_options)
+      block = options[:block]
+
+      # Symbol#to_proc creates procs with signature [[:req], [:rest]]
+      # These procs forward ALL arguments to the method, which causes
+      # issues when we call block.call(object, local_options) because
+      # it becomes object.method_name(local_options), and most methods
+      # don't accept extra arguments.
+      #
+      # For Symbol#to_proc, we only pass the object.
+      # For regular blocks, we pass both object and local_options.
+      if symbol_to_proc?(block)
+        block.call(object)
+      else
+        block.call(object, local_options)
+      end
+    end
+
+    private
+
+    def symbol_to_proc?(block)
+      # Symbol#to_proc has a characteristic signature:
+      # - Parameters: [[:req], [:rest]] (one required + rest args)
+      # - This is different from regular blocks which typically have
+      #   optional parameters like [[:opt, :obj], [:opt, :options]]
+      block.parameters == [[:req], [:rest]]
     end
   end
 end

spec/integrations/base_spec.rb

@@ -55,6 +55,63 @@
       end
     end
 
+    context 'when using Symbol#to_proc syntax' do
+      let(:obj) { object_with_attributes }
+
+      context 'with field using &:method_name' do
+        let(:blueprint) do
+          Class.new(Blueprinter::Base) do
+            identifier :id
+            field :name, &:first_name
+            field :job_position, &:position
+          end
+        end
+
+        it 'renders the field by calling the method on the object' do
+          result = JSON.parse(blueprint.render(obj))
+          expect(result['id']).to eq(1)
+          expect(result['name']).to eq('Meg')
+          expect(result['job_position']).to eq('Manager')
+        end
+      end
+
+      context 'with identifier using &:method_name' do
+        let(:blueprint) do
+          Class.new(Blueprinter::Base) do
+            identifier :user_id, &:id
+            field :first_name
+          end
+        end
+
+        it 'renders the identifier using Symbol#to_proc' do
+          expect(blueprint.render(obj)).to eq('{"user_id":1,"first_name":"Meg"}')
+        end
+      end
+
+      context 'when mixing Symbol#to_proc and regular blocks' do
+        let(:blueprint) do
+          Class.new(Blueprinter::Base) do
+            identifier :id
+            field :name, &:first_name
+            field :full_name do |obj|
+              "#{obj.first_name} #{obj.last_name}"
+            end
+            field :info do |obj, options|
+              "#{obj.position} (options: #{options.inspect})"
+            end
+          end
+        end
+
+        it 'handles both block types correctly' do
+          result = JSON.parse(blueprint.render(obj))
+          expect(result['id']).to eq(1)
+          expect(result['name']).to eq('Meg')
+          expect(result['full_name']).to eq('Meg Ryan')
+          expect(result['info']).to include('Manager')
+        end
+      end
+    end
+
     context 'Outside Rails project' do
       context 'Given passed object has dot notation accessible attributes' do
         let(:obj) { object_with_attributes }